This is something I first noticed about a year ago, give or take. Like, I’ll say “the sky is purple” and someone will respond with “it’s blue?” Why do people do that?
It’s such a strange thing for me, because I’m used to question marks being used for questions, not statements. It feels like at some point, I accidentally fell into an alternate dimension where this is considered a normal use of punctuation.
I know English is a continually-evolving language, so things like this shouldn’t be unexpected. Even still, this development feels bizarre to me.
I see your logic. I still wonder how this became popular though. Is it just one of those things people have been doing for a long time that I didn’t notice, and then one day I noticed it and I started seeing it everywhere?
I think its always been around. It might be more common to see it without further qualification (IE, “It’s blue, isn’t it?”), possibly because of the popularity of short-form content, but I don’t think its a new thing.